package org.nokatag.code;

public class PerlinNoise
{

    static int p[] = {
        151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 
        96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 
        69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 
        6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 
        94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 
        33, 88, 237, 149, 56, 87, 174, 20, 125, 136, 
        171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 
        27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 
        60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 
        245, 40, 244, 102, 143, 54, 65, 25, 63, 161, 
        1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 
        18, 169, 200, 196, 135, 130, 116, 188, 159, 86, 
        164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 
        226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 
        255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 
        58, 17, 182, 189, 28, 42, 223, 183, 170, 213, 
        119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 
        101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 
        19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 
        112, 104, 218, 246, 97, 228, 251, 34, 242, 193, 
        238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 
        145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 
        181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 
        50, 45, 127, 4, 150, 254, 138, 236, 205, 93, 
        222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 
        78, 66, 215, 61, 156, 180, 151, 160, 137, 91, 
        90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 
        7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 
        37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 
        234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 
        117, 35, 11, 32, 57, 177, 33, 88, 237, 149, 
        56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 
        74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 
        158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 
        220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 
        143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 
        209, 76, 132, 187, 208, 89, 18, 169, 200, 196, 
        135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 
        173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 
        5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 
        207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 
        28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 
        44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 
        172, 9, 129, 22, 39, 253, 19, 98, 108, 110, 
        79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 
        97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 
        191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 
        239, 107, 49, 192, 214, 31, 181, 199, 106, 157, 
        184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 
        150, 254, 138, 236, 205, 93, 222, 114, 67, 29, 
        24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 
        156, 180
    };

    public PerlinNoise()
    {
    }

    public static double noise2D(double x, double y)
    {
        double fx = Math.floor(x);
        double fy = Math.floor(y);
        int ix = (int)fx & 0xff;
        int iy = (int)fy & 0xff;
        x -= fx;
        y -= fy;
        int i = p[ix];
        int j = p[ix + 1];
        double u = fade(x);
        double v = fade(y);
        double grad1 = grad(p[i + iy], x, y);
        double grad2 = grad(p[j + iy], x - 1.0D, y);
        double grad3 = grad(p[i + iy + 1], x, y - 1.0D);
        double grad4 = grad(p[j + iy + 1], x - 1.0D, y - 1.0D);
        return lerp(v, lerp(u, grad1, grad2), lerp(u, grad3, grad4));
    }

    static double fade(double t)
    {
        return t * t * t * (t * (t * 6D - 15D) + 10D);
    }

    static double grad(int hash, double x, double y)
    {
        int h = hash & 3;
        double u = (h & 1) != 0 ? -x : x;
        double v = (h & 2) != 0 ? -y : y;
        return u + v;
    }

    public static double lerp(double t, double a, double b)
    {
        return a + t * (b - a);
    }

}
